Last Updated on September 25, 2025 by Melissa Lazaro

ISO/IEC 17043 vs. ISO/IEC 17025: Key Differences Explained

If you work in a laboratory, manage quality systems, or support organizations through ISO accreditation, chances are you’ve come across both ISO/IEC 17025 and ISO/IEC 17043. And if you’ve ever found yourself asking, “Wait—aren’t they pretty much the same thing?” you’re not alone.

Let’s clear that up.

In my years working with both laboratories and proficiency testing (PT) providers, I’ve seen this confusion pop up in internal audits, management review meetings, and even during ISO/IEC 17025 assessments. The two standards sound similar—and they both live in the world of competence and quality—but they serve entirely different purposes.

This article breaks it all down: what each standard is, who it applies to, how they differ, and how they actually work together. By the end, you’ll have a crystal-clear picture of when, where, and why to apply each one.

What Is ISO/IEC 17025?

The backbone of laboratory competence

Let’s start with the one most labs are familiar with: ISO/IEC 17025:2017.

This standard sets out the general requirements for the competence of testing and calibration laboratories. In short, it tells the world: “We know what we’re doing, we have the right equipment, our methods are valid, and our results can be trusted.”

Here’s what ISO/IEC 17025 focuses on:

• Validating your test and calibration methods
• Ensuring your measurement results are accurate, traceable, and consistent
• Maintaining impartiality and confidentiality
• Managing risks, nonconformities, internal audits, and corrective actions
• Training and qualifying your staff
• Implementing a quality management system geared toward lab activities

This standard applies to all types of labs—whether you’re testing drinking water, calibrating pressure gauges, or analyzing pharmaceutical samples. Accreditation to ISO/IEC 17025 means that your lab can consistently produce technically valid results.

Real example:

I once worked with a small environmental lab that specialized in testing soil for agricultural clients. They had great scientists, strong internal processes, and invested heavily in equipment calibration. But they needed ISO/IEC 17025 to gain recognition with government agencies and large corporate clients. Once they got accredited, their testing reports began opening doors—because the standard backed up the credibility they already had.

What Is ISO/IEC 17043?

The standard that keeps proficiency testing trustworthy

Now let’s talk about ISO/IEC 17043:2023. Unlike 17025, this standard isn’t for laboratories—it’s for proficiency testing providers.

Here’s what that means.

Proficiency testing (PT) is how laboratories evaluate their own performance. You sign up, receive a blind test item or sample, perform your usual analysis, and submit the results. Then the PT provider compares your results with other labs and tells you how you did.

But what if the PT provider doesn’t design the scheme properly? What if their scoring is inconsistent, or they don’t follow up when something goes wrong?

That’s why ISO/IEC 17043 exists. It sets out the general requirements for the competence of organizations that provide PT schemes.

It focuses on:

• Planning PT schemes with clear objectives and technical integrity
• Distributing samples and instructions in a controlled, unbiased way
• Evaluating participant performance using statistical methods
• Handling participant data confidentially
• Running schemes impartially—with no favoritism, no shortcuts
• Reviewing and improving PT scheme effectiveness over time

When a PT provider is accredited to ISO/IEC 17043, you can trust that their schemes are fair, reliable, and scientifically valid. And that matters because PT is often used as evidence during ISO/IEC 17025 assessments.

Real example:

I worked with a calibration lab that participated in multiple PT schemes. They had strong scores—but when the assessor reviewed their PT records, they noticed the provider wasn’t ISO/IEC 17043-accredited. There was no clear scoring method and no evidence that the scheme itself was independently reviewed. As a result, the lab had to repeat testing through an approved provider—just to meet audit requirements. The problem wasn’t the lab’s performance—it was the scheme’s credibility.

ISO/IEC 17043 vs. ISO/IEC 17025 – A Side-by-Side Comparison

Now that we’ve unpacked each standard, let’s compare them directly.

Feature	ISO/IEC 17025	ISO/IEC 17043
Purpose	Competence of testing and calibration labs	Competence of PT scheme providers
Applies To	Laboratories performing testing or calibration	Organizations that design and deliver PT
Main Goal	Ensure lab results are valid, repeatable, and traceable	Ensure PT results are fair, statistically valid, and impartial
End User	Lab clients, regulatory bodies, accreditation bodies	Laboratory participants, accreditation bodies
Outcome	Accreditation shows lab can deliver reliable results	Accreditation shows PT provider can deliver credible evaluations
Relationship to Each Other	Participating in PT is a requirement	Providing PT supports labs in meeting that requirement

Think of it like this:

• ISO/IEC 17025 is for labs doing the actual measurements.
• ISO/IEC 17043 is for the people testing the testers.

They don’t replace each other. They work together.

How These Standards Complement Each Other in Practice

Here’s why this comparison matters in real life.

ISO/IEC 17025 includes a requirement for labs to monitor the validity of their results. One of the main tools for doing that is participation in proficiency testing. But here’s the catch—just signing up for any PT scheme doesn’t meet the requirement.

Accreditation bodies now expect labs to participate in PT from ISO/IEC 17043-compliant providers. Otherwise, how can anyone trust the evaluation?

This means your lab’s ISO/IEC 17025 system is only as strong as the PT you use to back it up.

Client story:

A clinical lab I worked with was using a regional PT provider who had good reviews but no formal accreditation. When they submitted those reports during their 17025 audit, the assessor asked for proof that the provider followed valid scoring methods. The lab couldn’t provide it. The result? A nonconformity and a rush to find an alternate scheme—one that was already 17043-accredited.

It’s not just about good performance. It’s about the credibility of how that performance is measured.

Pro Tips for Labs and PT Providers

Pro Tip 1: If you’re a lab, verify your PT provider’s ISO/IEC 17043 accreditation

Don’t just check the certificate—read the scope. Make sure it covers the test types you’re participating in.

Pro Tip 2: If you’re a PT provider, don’t use ISO/IEC 17025 as your design blueprint

17043 has unique requirements—especially around impartiality, scheme review, and statistical evaluation. Adapting 17025 procedures won’t cut it.

Pro Tip 3: For internal PT or inter-lab schemes, use 17043 as your structure

Even if you’re not formally accredited, modeling your internal PT program on 17043 helps ensure it’s fair, useful, and defensible.

Pro Tip 4: During audits, be ready to show how you evaluated PT provider competence

This could be a documented review of accreditation, technical protocols, or historical performance. Don’t leave it to verbal assurance.

Common Misunderstandings and FAQs

“Can a lab be accredited to ISO/IEC 17043?”
No. ISO/IEC 17043 is for PT providers, not testing or calibration laboratories.

“Is PT required under ISO/IEC 17025?”
Yes. Laboratories are expected to regularly participate in appropriate PT or interlaboratory comparisons to demonstrate validity of their results.

“What if no ISO/IEC 17043-accredited PT provider is available?”
In rare cases, labs can use non-accredited providers—but they need to document the reason and evaluate the provider’s competence themselves. Some accreditation bodies will expect a formal risk assessment and alternate quality checks.

Different Roles, Shared Purpose

ISO/IEC 17025 and ISO/IEC 17043 are two very different standards—but they both aim to protect confidence in test results. One ensures that labs are competent. The other ensures that the tools used to assess those labs—proficiency testing—are also competent.

Understanding the difference means you’ll make better decisions when choosing PT schemes, preparing for audits, or designing internal comparison programs.

It’s not about memorizing clauses—it’s about knowing what role each standard plays in your quality system.

Need help reviewing your PT program or choosing an accredited provider?
Let’s talk. I’ve helped both labs and PT providers build and align systems that stand up to scrutiny—and I’d be happy to help you do the same.